Field
Aspects of the present disclosure relate to air-to-ground communication systems, and more particularly to an air-to-ground communications system adapted for use with an airborne mobile platform that provides an ultra-low profile conformal aircraft antenna.
Background
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. Such networks are terrestrial-based networks, however, in recent years, publicly accessible networks are being made available for passengers on commercial air transportation, e.g., airplanes and other aircraft.
Such services are known as air-to-ground (ATG) communication services, and may provide such services as broadband data, voice communication, and entertainment such as streaming movies or music. Although ATG services and networks are similar to currently deployed terrestrial cellular and other wireless networks, there are aspects of ATG networks that differ from these networks.
As aircraft fly across a geographic region, each aircraft is serviced by a particular base transceiver station (BTS) until signal quality, signal strength, or available bandwidth from that BTS is insufficient, at which time service is transferred to another BTS. Such a transfer can be referred to a “handoff,” similar to handoffs that occur in terrestrial cellular networks for cellular devices (handsets, PDAs, etc.) when such devices are mobile.
Aircraft may use a single transceiver having an antenna mounted on the undercarriage of the aircraft to communicate with the BTS. However, BTS antenna patterns are usually designed to service terrestrial customers, and the beam patterns at a given BTS are usually not arranged to service ATG communications traffic.
Current generation satellite communications systems offering broadband internet service to commercial jetliners specify sophisticated high gain agile beam antennas to initiate and maintain the communications link to the satellites. These antennas are large, complex, and expensive, and involve large surface areas and volumes on the aircraft fuselage, adding to installation costs.
Capacity for these systems is limited. Launching new satellites to accommodate capacity growth can be prohibitively expensive. Generally, these costs are passed on to the consumer in the form of high service fees. The present disclosure describes aspects of a low cost aircraft antenna solution that supports an air to ground communications system. The system offers broadband internet service that is similar to or exceeds that of the more expensive satellite based systems, but at a fraction of the cost of current antenna technologies servicing these sat-com based systems.
Merely replicating terrestrial cellular beam patterns or satellite antenna beam patterns around the aircraft in an omnidirectional pattern, however, would provide insufficient signal strength and capacity to service the thousands of aircraft and potentially hundreds of thousands of users in such an ATG system. Replicating the terrestrial beam patterns would also create interference patterns that could be deleterious to communications links in ATG systems as well as other aircraft communications systems.
As aircraft travel through a particular BTS service area, or are handed off to another BTS service area, the aircraft antenna may also need to change beam patterns or beam directions. The change provides continuous service during aircraft flight, which may not have been needed or have as stringent tracking accuracy as with satellite communications links. Federal Communication Commission (FCC) rules may also prohibit certain portions of the flight from providing communications services. FCC rules may prevent transmissions in specific terrestrial directions that may not have been at issue when the transmissions were directed to higher elevations.
Further, adding additional externally mounted items to an aircraft fuselage affects aircraft flight characteristics, which makes implementation of external aircraft antennas difficult for ATG systems.